Methods and systems to keep a work piece surface free from liquid accumulation while performing liquid-jet guided laser based material processing

ABSTRACT

A gas flow can be provided together with a liquid jet guided laser beam to remove accumulated liquid on the processing surface. The gas flow can be configured to have minimum interference with the liquid jet guided laser beam, while functions to blow away liquid generated by the liquid jet. Keeping the surface free from accumulated liquid can improve the efficiency of the liquid jet guided laser processing.

This present application claims priority from U.S. Provisional PatentApplication Ser. No. 61/915,510, filed on Dec. 13, 2013, entitled:“Methods and systems to keep a work piece surface free from liquidaccumulation while performing liquid-jet guided laser based materialprocessing” which is incorporated herein by reference.

BACKGROUND

Laser technology is applied for a large variety of material processingtasks, such as cutting, drilling, welding, marking, engraving andmaterial ablation. Nearly all materials can be processed, e.g. metals,metal alloys, ceramics, diamonds, synthetic diamonds, carbon fibres,sapphire, quartz, glass, plastics and more. In almost every case, thelaser light is focused into a very small spot onto the work piece usinga focusing lens, to enable the processing task by generating sufficientenergy on the work piece. The work piece therefore has to be preciselyaligned into the laser focus throughout the processing task.

Liquid-jet guided laser technology, as for example described in patentEP 1940579B1 and U.S. Pat. No. 8,859,988B1, couples the laser focus intoa small liquid-jet, for example, through a focusing lens. This couplingtakes place in a coupling unit. The coupling unit can include a metalchamber that on the side of the focusing lens is closed with a laserprotection window. On the opposite side the chamber carries a nozzle.Liquid provided to the coupling unit flows between window and nozzle andleaves the nozzle in form of a liquid-jet. The energy of the laser spotin the focal plane is captured inside the liquid-jet and guided to thework piece through internal reflection. This method eliminates thenecessity to control the distance of the work piece precisely becausethe required energy to perform the processing is available throughoutthe laminar length of the liquid-jet. Any liquid that provides suitablelight guide capabilities can be used to form the liquid-jet.

To increase the laminar length of the liquid-jet, and with that theworking distance of the process, an assist gas can be provided to theliquid-jet as described in patent EP 1940579B1 or patent EP 1833636B1.The assist gas is provided and guided as a direct boundary layer to theliquid-jet in order to reduce the resistance between liquid and ambientair and thereby increase the laminar length of the liquid-jet. Thus theliquid jet is surrounded by the assist gas to leave the coupling unitthrough the same exit opening. Inside the coupling unit, the assist gasis directed perpendicular to the liquid jet. For example, the assist gasis in the horizontal plane hitting the liquid-jet that is travelling inthe vertical plane. The assist gas and the liquid jet then leave thesystem at a same exit hole, with the liquid jet in the middle surroundedby the assist gas.

FIG. 1 illustrates a prior art liquid jet guided laser beam systemhaving an assist gas configuration. A liquid jet guided laser beamsystem 100 can include a coupling unit 130 having a nozzle 135. Aliquid, such as water 120, can be provided to the nozzle 135, and travelthrough the hole of the coupling unit to form a liquid jet 140 in achamber 160. A laser beam 110 can be focused, for example, by a lens115, to the liquid jet 140. Internal reflection can limit the laser beamto be within the liquid jet. The liquid jet guided laser beam can flowtoward an object surface 190, where the laser can cut through the objectby means of material ablation in a single or multiple passes.

An assist gas 150 can be provided to a cavity 160 of the coupling unit130. The assist gas 150 can flow 155 in a direction perpendicular to theliquid jet 140, but do not intersect the liquid jet. The assist gas 155can envelop the liquid jet, reducing the friction of the liquid jet tothe air ambient, and potentially extending the laminar length of theliquid jet. The properties of the assist gas can be chosen to optimizethe laminar length of the liquid jet, such as low viscosity gas atmedium pressure.

Since the assist gas 150 and the liquid jet 140 are mixed in a samechamber 160, there is dependency between the assist gas and the liquidjet. For example, the pressure and flow properties of the assist gas canbe selected to optimize the laminar flow of the liquid jet. Otheroperating conditions of the assist gas can adversely affect the liquidjet. For example, a high pressure of the assist gas can shorten thelaminar flow of the liquid jet, and an even higher pressure of theassist gas can destroy the liquid jet.

There is a need for improving the liquid-jet laser technology, forexample, to keep a work piece surface free from liquid accumulationwhile performing liquid-jet guided laser based material processing.

SUMMARY OF THE EMBODIMENTS

In some embodiments, the present invention discloses methods and systemsfor keeping a surface dry when being processed with a liquid jet guidedlaser beam. A gas flow can be provided, which surrounds the liquid jetand runs in a same direction as the liquid jet. The gas flow can clearthe surface from accumulated liquid, which can improve the efficiency ofthe liquid jet guided laser processing. The gas flow and the liquid jetcan be generated at two separate openings, allowing the independentcontrol of the gas flow characteristics, such as pressure or flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art liquid jet guided laser beam systemhaving an assist gas configuration.

FIGS. 2A-2B illustrate effects of an air jet according to someembodiments.

FIGS. 3A-3C illustrate effects of an air jet according to someembodiments.

FIGS. 4A-4C illustrate a schematic operation of a liquid jet guidedlaser beam having a air jet according to some embodiments.

FIGS. 5A-5C illustrate different configurations of the air jet accordingto some embodiments.

FIGS. 6A-6C illustrate different flow directions of the air jetaccording to some embodiments.

FIGS. 7A-7B illustrate flow charts for running a liquid jet guided laserbeam according to some embodiments.

FIG. 8 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments.

FIGS. 9A-9C illustrates a schematic of different air jets according tosome embodiments.

FIG. 10 illustrates a liquid jet guided laser system including acoupling unit having an air jet nozzle according to some embodiments.

FIGS. 11A-11D illustrate a schematic of a coupling unit for liquid jetguided laser processing according to some embodiments.

FIG. 12 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments.

FIG. 13 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments.

FIGS. 14A-14B illustrate a coupling unit for a liquid jet guided lasersystem according to some embodiments.

FIG. 15 illustrates a schematic of a coupling unit for liquid jet guidedlaser processing according to some embodiments.

FIGS. 16A-16B illustrate flow charts for operating a liquid jet guidedlaser beam using a air jet according to some embodiments.

FIGS. 17A-17B illustrate a schematic of another coupling unit for liquidjet guided laser processing according to some embodiments.

FIG. 18 illustrates a schematic of another coupling unit for liquid jetguided laser processing according to some embodiments.

FIGS. 19A-19B illustrate flow charts for operating a liquid jet guidedlaser system according to some embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In some embodiments, the present invention discloses methods and systemsfor liquid-jet guided laser beam material processing while keeping thework piece surface free from liquid accumulation. A gas flow can beprovided together with the laser beam. The gas flow can be a air jet,which can prepare the surface of the object that the liquid-jet guidedlaser beam processes. The gas flow can be an air jet, which can bedirected toward the working area of the laser beam, and can be operableto reduce the amount of liquid accumulated by the liquid jet at thesurface of the work piece. The air jet can be configured to have gaspressure and flow velocity when leaving the gas nozzle to clear theobject surface of the fluid, such as driving away the liquid to exposethe work piece surface. Further, the air jet can be configuredindependent of the liquid jet, thus can minimize any interference to theliquid-jet.

In the following description, the term air jet can include a gas flow,such as a flow of air or of any other gases, such as nitrogen, argon, oroxygen. Thus the term “air jet” in the context of the present inventionis not limited to a jet of air, but also includes a flow of a gas or afluid, such as a nitrogen gas flow, or an aerosol flow.

The air jet can be used with liquid jet guided laser beam with orwithout an assist gas. The air jet can provide functionalities that theassist gas cannot perform. For example, the assist gas cannot clear aconcave surface such as a cavity that can hold the liquid. The air jet,since the pressure can be independently adjusted, can clear the worksurface from accumulated liquid, e.g., concave or convex surfaces. Forexample, due to the functionality of the assist gas, which is toincrease the laminar length of the liquid jet, the assist gas haslimited working pressure and flow ranges, and therefore cannot clearliquid off the work piece surface. Due to the configuration of theassist gas flow in relation to the liquid jet, which forms 90 degreeangle with each other, high pressure can destroy the liquid-jet becauseof its large incident angle to the liquid-jet.

In some embodiments, the air jet can be configured to surround theliquid jet and run in a same direction, such as parallel orsubstantially parallel, with the liquid jet. In the followingdescription, detailed description of parallel air jet is provided asexamples of typical air jet directions. But the present invention is notso limited, and an air jet can run in a same direction as the liquidjet, e.g., parallel as well as making an angle between −90 and +90degrees from the liquid jet direction, such as between −15 degrees(e.g., 15 degrees toward the liquid jet) to +45 degrees (e.g., 45degrees away from the liquid jet), including −10, −5, 0, 5, 10, 15, 20,25, and 25 degrees. The air jet can be produced separately from theliquid jet, e.g., the air jet can run parallel to and surrounding theliquid jet while being separated from each other by a solid separationin the coupling unit. Thus the air jet can be independently controlledwithout or with minimum effect on the liquid jet operation. The air jetand the liquid jet can leave the system, e.g., the coupling unit, at twoseparate openings, such as a middle opening for the liquid jet and asurrounding opening for the air jet. In some embodiments, an assist gasbe included, for example, the liquid jet can be enveloped in the assistgas, and both the assist gas and the liquid jet can emerge from thesystem, e.g., the coupling unit, at a same opening.

In some embodiments, the air jet can allow the laser beam to directlyprocess the material, without the potential interference from any liquidaccumulated at the working area. The air jet can reduce the liquid atthe surface of the work piece, such as keeping the surface dry tooptimize the efficiency of the liquid jet guided laser beam. Forexample, by reducing the amount of liquid at the surface, backreflection in the direction of the processing head exit can be minimizedor eliminated. Further, the liquid quality of the liquid jet at thecontact point to the surface can be increased, e.g., not being affectedby the liquid accumulated at the surface.

In some embodiments, the air jet can improve the operation of the liquidjet guided laser beam, for example, by removing liquid mist, or liquiddrop accumulated from the liquid mist, from the liquid jet. For example,during the processing of the work piece, liquid mist can appear on theexit side of the coupling unit of the laser cutting head. The liquidmist can cumulate and fall down in the form of a liquid drop. Due to thesurface tension of the liquid, such drops can be pulled toward, e.g.,approaching, the actual liquid-jet. Upon release of such drop, theliquid-jet will be disrupted for a short period, which can be causedstop the laser processing of the work piece during such disruption ofthe liquid-jet. The exit side of the coupling unit can be mechanicallyformed to allow gravity to pull the liquid drops away from theliquid-jet, some liquid drops can still be pulled toward the liquid-jet,for example, due to the strong surface tension of some liquids.

In some embodiments, the air jet can improve liquid jet guided laserprocessing inside cavities of 3-dimensional work pieces. During theprocessing, such cavities can be quickly filled up with liquid, e.g.,from the liquid jet. The actual liquid jet then needs to penetratethrough a liquid film before reaching the surface of the work piece.Such liquid film can be a few millimetres up to multiple centimetreshigh. Such liquid film can destroy the liquid to ambient barrier that isrequired for adequate guiding of the light in the liquid-jet by internalreflection. The kinetic energy of the liquid-jet can not be sufficientto maintain such a liquid to ambient barrier. The air jet can beoptimized to clear the liquid film in such cavities, at least in theworking area of the liquid jet. The liquid jet can process the workpiece at 3-dimensional configurations without being affected. Theliquid-jet pressure and air jet pressure can be independently controlledfor this purpose.

FIGS. 2A-2B illustrate effects of an air jet according to someembodiments. In FIG. 2A, liquid 290 can be accumulated in a cavity 292of a workpiece 294. Laser beam 270 can be internally reflected in aliquid jet 240. Due to the accumulated liquid 290, the laser beam can bediverged 277 to the accumulated liquid 290, due to the absence of anair-liquid interface that is necessary for the internal reflectionguidance. The diverged laser beam can lower the amount of laser energydirected toward the workpiece surface for processing, such as cutting.

In FIG. 2B, an air jet 230 can be provided together with the liquid jet240. The air jet can be formed by providing a flow of gas or gas/liquidmixture. The air jet can clear the accumulated liquid, e.g., pushing theliquid 295 away from the liquid jet to present a surface free of liquidunder the liquid jet. The laser power can be internally reflected to thesurface of the workpiece, with minimal or no laser power loss. The airjet can be independent of the liquid jet, having a high range ofpressure or flow without affecting the operation of the liquid jet.

In some embodiments, the air jet can be configured to surround theliquid jet. The surrounded air jet can clear the working area of theliquid jet, e.g., removing liquid at the area that the laser beam,embedded in the liquid jet, need to contact the workpiece surface. Theair jet can blow away liquid also at the deep cut, which can easily haveliquid accumulated therein.

FIGS. 3A-3C illustrate effects of an air jet according to someembodiments. FIG. 3A shows a cross section view perpendicular to a cut310 in a cavity 392 of a workpiece 394, showing a short side of the cut310. FIG. 3B shows a corresponding top view of the cut 310. FIG. 3Cshows a corresponding cross section view along the cut 310, showing along side of the cut 310. A liquid jet 340 can reach the bottom side ofthe cavity 392, cutting through the material of the workpiece 394 toform the cut 310. An air jet 320, which surrounds the liquid jet 340,runs along the liquid jet 340 to push liquid 390 away from the workingarea 345 of the laser beam embedded in the liquid jet. The air jet canclear the liquid even in a portion of the cut 310, exposing the workingarea 345 so that the laser beam can contact the surface of the workpiecewithout being diverged from the liquid jet.

In some embodiments, the air jet can be used together with the assistgas. The assist gas can be configured to optimize a laminar length ofthe liquid jet, and the air jet can be configured to optimize a surfacepreparation of the work piece. For example, it would be difficult to usethe assist gas to prevent a cavity from being flooded with liquid,because the optimal assist gas pressure is not sufficient to remove theliquid from the cavity. A modification of the assist gas, such asincreasing the assist gas pressure beyond the optimum working range,would destroy or strongly reduce the liquid-jet laminar length.

In some embodiments, the present invention discloses systems and methodsto keep the work piece surface free from liquid accumulation whileperforming liquid-jet guided laser based material processing, which thencan allow the liquid-jet to reach the work piece surface directly. A airjet can be provided, which can strike the work piece surface in avicinity of the liquid jet with controllable pressure and flow to reduceor clear any liquid accumulated on the surface. The air jet can beconfigured to reduce or eliminate any liquid-jet interruptions orsplashes caused by liquid mist drops that are pulled to the liquid-jetby surface tension. For example, by running the air jet in the samedirection such as parallel and surrounding the liquid jet, the liquidmist drops can be attracted toward the air jet. Further, the surroundedparallel air jet can also assist in improving the laminar flow length ofthe liquid jet, for example, to provide an independent control of assistgas pressure in relation to its effect on the laminar length of theliquid-jet.

FIGS. 4A-4C illustrate a schematic operation of a liquid jet guidedlaser beam having an air jet according to some embodiments. In FIG. 4A,a liquid source 400, such as a water flow source, is configured togenerate a liquid jet 440. A laser beam can be embedded in the liquidjet 440, which can strike an object surface 490 for processing theobject, such as cutting the object. A gas source 410, such as acompressed air, gas or fluid source, is configured to generate an airjet 420. As discussed above, an air jet can also be called a gas jet ora fluid jet, including a flow of a gas or a gas/fluid mixture. Aseparator 460 can be included to separate the liquid jet 440 and the airjet 420, at least at a beginning portion of the liquid jet and air jet.The separator can provide independent controls of the liquid jet and airjet, e.g., high pressure and high flow of the air jet can have no orminimum effect of the operation of the liquid jet

In FIG. 4B, a liquid source 402 and a gas source 412 can be twoindependent and separate units. For example, the liquid source 402 canprovide a liquid flow through a coupling unit to generate a liquid jet442. A laser source can be included for focusing a laser beam to theliquid jet and guided by the liquid jet toward the object surface 492.An assist gas source can be optionally included, enveloping and exitingat a same opening as the liquid jet. The assist gas conditions can beselected to optimize the laminar flow length of the liquid jet. The gassource can provide an air jet 422, which can strike the object surfaceat a vicinity of the liquid jet.

In FIG. 4C, a gas source 414 can be embedded, but independent, from aliquid source 404. An air jet 424 can run in the same direction such asto the liquid jet 444, and thus can strike the object surface at an areaclose to the area struck by the liquid jet.

In some embodiments, the characteristics of the air jet 424 can bechosen to clear the object surface from accumulated liquid. For example,the object can have a 3 dimensional feature 494 that can form a cavityto contain liquid. Thus liquid from the liquid jet can accumulate in thecavity, forming a liquid film that can hinder or interfere with theoperation of the liquid jet, for example, by destroying the liquidcolumn that confines the laser beam. The air jet 424 can clear theliquid film, pushing the liquid 450 away from the working area 455. Theair jet 424 thus can prepare the surface of the object, removing anyaccumulated liquid to provide a suitable surface for the liquid jetguided laser beam 414.

FIGS. 5A-5C illustrate different configurations of the air jet accordingto some embodiments. A system 500 can generate a liquid jet guided laserbeam 540 toward an object surface 590. The system 500 can optionallygenerate an assist gas flow enveloping the liquid jet guided laser beam540. The assist gas configuration can be optimized for improve thelaminar flow of the liquid jet, and can exit the system 500 at a sameopening as the liquid jet.

In FIG. 5A, a gas source 520 can be integrated to system 500 to generatea air jet 530. The air jet 530 can run in the same direction such asparallel with the liquid jet 540, and can surround the liquid jet 540,such as forming a concentric flow surrounding the liquid jet 540. Theair jet 530 and the liquid jet 540 can exit the system 500 at separateopenings, e.g., there are two separate nozzles for the liquid jet andthe air jet, with the nozzle for the air jet forming an envelope aroundthe nozzle for the liquid jet. The concentric feature of the liquid jetand the air jet can provide a radial symmetric configuration, which canbe effective in improving the operation of the liquid jet guided laserbeam. Concentric walls can be used to separate the air jet 530 from theliquid jet 540, at least in the system 500 before the air jet and theliquid jet leaving the system 500.

FIGS. 5B and 5C show alternative configurations for the air jet. The airjet can be configured to run in the same direction such as parallel tothe liquid jet. In FIG. 5B, a separate air jet source 522 can be used,which can generate a air jet 532 for the liquid jet 540. In FIG. 5C, anair jet source 524 can be integrated to the system 500, which cangenerate a parallel air jet 534. Different conduits can be used toseparate the air jet 532/434 from the liquid jet 540, at least in thesystem 500 before the air jet and the liquid jet leaving the system 500.

In some embodiments, the air jet can form an angle with the liquid jet,for example, to optimize the operation of the liquid jet guided laseroperation. In general, an air jet can be provided so that the air jetimpacts the surface of the workpiece at a location at or near thelocation that the liquid jet impacts the surface. Due to the potentialinterference between the air jet and the liquid jet outside of theliquid and gas sources, the air jet can be diverged from the liquid jet.

FIGS. 6A-6C illustrate different flow directions of the air jetaccording to some embodiments. In FIG. 6A, for a workpiece 691 that canbe placed near, e.g., a small distance 651 (about less than 2 cm, lessthan 1 cm, or less than 0.5 cm) to the liquid jet guided laser system601, the air jet 631 can be directed toward the liquid jet 641, such asbetween 0 and −20 degrees, or between 0 and −10 degrees. The anglebetween the air jet and the liquid jet can be defined as a negativeangle if the air jet is directed toward the liquid jet from thedirection from the laser system to the workpiece, as shown in FIG. 6A.The small distance 651 can be used if the workpiece is concave down orflat, allowing the laser system to travel across the workpiece withoutinterference. In addition, the air jet can have low pressure and lowflow due to the small distance. For example, operating conditions (suchas pressure and flow) of a gas source can be regulated to generate anair jet having low pressure and low flow.

In FIG. 6B, for a workpiece 692 that can be placed a little farther,e.g., a medium distance 652 (about less than 6 cm, less than 2 cm, orless than 1 cm) to the liquid jet guided laser system 602, the air jet632 can be directed substantially parallel to the liquid jet 642, suchas deviating less than 1 or 2 degrees from the parallel direction. Themedium distance 652 can be used if the workpiece is flat, allowing thelaser system to travel across the workpiece without interference. Inaddition, the air jet can have medium pressure and medium flow due tothe medium distance. For example, operating conditions (such as pressureand flow) of a gas source can be regulated to generate an air jet havingmedium pressure (such as less than 6 bar or less than 2 bar pressure)and medium flow (such as less than 6 or less than 2 standard liters perminute).

In FIG. 6C, for a workpiece 693 that can be placed far, e.g., a largedistance 653 (about greater than 1 cm, greater than 6 cm, or greaterthan 10 cm) to the liquid jet guided laser system 603, the air jet 633can be directed away from the liquid jet 643, such as between 0 and 45degrees, or between 0 and 30 degrees. The angle between the air jet andthe liquid jet can be defined as a positive angle if the air jet isdirected away from the liquid jet from the direction from the lasersystem to the workpiece, as shown in FIG. 6C. The large distance 653 canbe used if the workpiece has irregular surface topology, such as acavity that recesses under a top surface of the workpiece. For largedistances 653, the air jet pressure of flow might need to be increased,for example, to travel the large distances 653 and to clear liquid froma cavity. For example, operating conditions (such as pressure and flow)of a gas source can be regulated to generate an air jet having highpressure (such as less than 10 bar or less than 6 bar pressure) and highflow (such as less than 10 or less than 6 standard liters per minute).The high pressure and flow can potential interfere with the liquid jet,for example, by shortening the laminar length of the liquid jet, ifrunning parallel or toward the liquid jet.

In some embodiments, the present invention discloses methods and systemsfor operating a liquid jet guided laser systems, including generating anindependent gas flow surrounding a liquid jet. The independent gas flowcan be a gaseous flow or a flow containing a mixture of a gas and aliquid, such as an aerosol flow. The independent gas flow can beconfigured to be independent with the liquid jet, e.g., having a widerange of operating conditions that do not significantly affect theoperation of the liquid jet. For example, the independent can have ahigh pressure, such as capable of running at 10 bar pressure or higherwithout significantly shorten the laminar length of the liquid jet. Theindependent flow configurations can be achieved by having a wall or apartition between the gas flow and the liquid jet, for example, inside acoupling unit, so that the gas flow and liquid jet can run with apartfrom each other, such as running substantially parallel or running awayfrom each other at a small angle (e.g., less than 30 degrees).

FIGS. 7A-7B illustrate flow charts for running a liquid jet guided laserbeam according to some embodiments. In FIG. 7A, operation 700 provides alaser beam embedded in a liquid jet, for example, generated from asystem having a laser beam focused on a liquid jet. The system canoptionally include an assist gas for optimizing the liquid jet laminarflow. The liquid jet can be directed toward an object, and can makecontact to the object surface. Operation 710 flows a gas flow, e.g., anair jet, to the object surface. The gas flow is configured to blowliquid away from the object surface. For example, the gas flow pressureand flow rate can be so that any liquid accumulated on the objectsurface is pushed away from the area that the liquid jet contacts theobject. The gas flow can be configured to not affect the liquid jet,such as not intersecting the liquid jet. The gas flow can be configuredto be independent of the liquid jet, e.g., having operating conditionsthat can be adjusted without having significant effect on the liquidjet.

In FIG. 7B, operation 730 emits a laser beam toward an object surface.The laser beam is guided by a liquid jet. Operation 740 flows a gas flowtoward the object surface. The gas flow is configured to run in the samedirection, such as substantially parallel to the liquid jet and notintersecting the liquid jet, and to surround the liquid jet. The gasflow is also configured so that a portion of the parallel run of the gasand liquid jet is separated by a separation, e.g., the gas flow and theliquid jet leave the system in two separate nozzles. The gas flowconditions are selected to blow liquid away from the object surface.

In some embodiments, the present invention discloses systems and methodsfor processing materials using a liquid jet guided laser. The methodscan include generating a air jet column that is guided concentrically,yet in-direct around the liquid jet. The system can include a mechanicalseparation inside the coupling unit for the air jet and the liquid jet.The air jet can be actively guided in the same direction as the liquidjet. The air jet can also allow the liquid-jet to interrupt the vacuumthat builds on the exit side of the nozzle by means of pulling a smallamount of air jet.

In some embodiments, the present invention discloses methods and systemsfor operating a liquid jet guided laser systems, including changingoperating conditions, such as direction, pressure and flow volume, ofthe air jet. For example, for flat or concave down workpiece, the lasersystem can run close to the workpiece surface, for example, to improvethe power transfer from the laser to the workpiece surface. The air jetdirection can be parallel with the liquid jet, or can be directed towardthe liquid jet. The gas pressure can be low, such as less than 5 bar,less than 2 bar, or less than 1 bar pressure. The gas flow can also below, such as less than 5 slm (standard liters per minute), less than 2slm, or less than 1 slm flow.

In some embodiments, different air jet nozzles can be used to providedifferent flow directions. For example, an air jet nozzle havingparallel walls, e.g., walls that are parallel to the liquid jet flowdirection, can be used to generate an air jet with parallel flow. An airjet nozzle having diverged walls, e.g., walls that spread out toward theexit port, can be used to generate an air jet with diverged flow, e.g.,flowing away from the liquid jet.

FIG. 8 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments. In operation 800, a topologydistance of a workpiece is determined. The topology can be determined asa maximum distance from a bottom surface of a cavity to a top surface ofthe workpiece. The top surface can be the highest surface of theworkpiece. The bottom surface can be the bottom surface of a cavity thatcan be processed by the laser system. In some embodiments, the depth ofthe desired cut can be taken into account, e.g., adding to the length ofthe topology distance. Thus the bottom surface that is to be processedby the laser system, of a deepest cavity can be selected to calculatethe maximum distance from the highest surface of the workpiece.Operation 810 sets a liquid jet guided laser system to achieve a liquidjet having a laminar length greater than the topology distance. Forexample, a laser system having a liquid jet with a laminar lengthgreater than the topology distance can be used to process the workpiece.In general, the laser system can be set above the highest surface of theworkpiece, and the liquid jet can travel from the laser system, e.g.,from the liquid nozzle in the coupling unit, toward and reaching thebottom surface of the cavities in the workpiece.

Operation 820 adjusts a pressure from a gas source to form an air jet tothe object surface to clear liquid away from the object surface. In someembodiments, the maximum pressure can be 10 bar or higher. The pressureof the gas source can be adjusted based on the topology distance of theworkpiece, and/or based on the liquid retaining capability of theworkpiece. For example, if the topology distance is small, e.g., lessthan 1 cm, and the workpiece does not accumulate much liquid, e.g., atilted flat workpiece so that the liquid drains away from the surface, alow pressure, e.g., less than 1 bar, such as between 0.05 bar to 1 bar,or between 0.5 bar to 1 bar, can be used. If the topology distance islarge, e.g., greater than 0.5 cm or 1 cm, for example, due to thepresence of deep cavities, the workpiece can accumulate liquid, forexample, in the cavities. A high pressure can be used to clear a portionof the surface from the accumulated liquid, for example, driving theliquid away from the area surrounding the liquid jet. The pressure canbe less than 10 bar, such as between 0.5 bar to 0 bar, or between 1 barto 10 bar.

Operation 830 adjusts a direction of the air jet to the object surfaceto reduce interference with the liquid jet. The angle of the air jet canbe adjusted based on the topology distance of the workpiece, and/orbased on the liquid retaining capability of the workpiece. The angle ofthe air jet can be adjusted by manually replacing an air jet nozzle,e.g., selecting an appropriate air jet nozzle based on air jet nozzleshaving different gas direction, such as parallel gas direction, divergedgas direction away from the liquid jet, or converged gas directiontoward the liquid jet.

For example, if the topology distance is small, e.g., less than 1 cm,and the workpiece does not accumulate much liquid, e.g., a tilted flatworkpiece so that the liquid drains away from the surface, a lowpressure, e.g., less than 1 bar, such as between 0.05 bar to 1 bar, orbetween 0.5 bar to 1 bar, can be used. If the topology distance islarge, e.g., greater than 0.5 cm or 1 cm, for example, due to thepresence of deep cavities, the workpiece can accumulate liquid, forexample, in the cavities. A high pressure can be used to clear a portionof the surface from the accumulated liquid, for example, driving theliquid away from the area surrounding the liquid jet. The pressure canbe less than 10 bar, such as between 0.5 bar to 0 bar, or between 1 barto 10 bar.

FIGS. 9A-9C illustrates a schematic of different air jets according tosome embodiments. A coupling unit can be configured to allow a liquidjet and an air jet to pass through in different conduits. For example,there can be a physical separation between the conduit that carries theliquid jet and the conduit that carries the air jet. Thus the air jetand the liquid jet can emerge from the coupling unit without anyinterference. For example, the air jet and the liquid jet can runparallel, or can form and angle so that the air jet and the liquid jetdo not intersect in the distance between the coupling unit and thesurface of the workpiece.

In some embodiments, the present invention discloses a liquid jet guidedlaser system for processing a workpiece. The liquid jet guided lasersystem can include a laser for emitting a laser beam, together with anoptical element, such as a mirror and/or a lens, for coupling the laserbeam with a liquid environment. The liquid environment can include anassembly to generate a liquid jet. The laser beam can be coupled to theliquid jet to form internal reflection in the liquid jet. The liquid jetcan be formed by a nozzle module, which can be configured to beconnected to a liquid supply line for forming a liquid jet. The liquidsupply line can include a liquid source, such as a water source or analcohol source, which is under a liquid pressure to generate a liquidflow to the nozzle module, for example, through a liquid inlet.

The liquid jet guided laser system can include an air jet module togenerate a gas flow (which can be a gas flow or a flow of a gas/liquidmixture). The gas flow can be configured to remove liquid at the workingsurface area of the liquid jet guided laser system, such as the surfacearea surrounding the liquid jet. Since the liquid jet carries a liquid,when the liquid jet contacts the workpiece surface, some liquid can beaccumulated at the workpiece surface. The accumulated liquid caninterfere with the operation of the liquid jet guided laser system, suchas eliminating or changing the location of the boundary condition of anair-liquid interface, which can result in a re-direction of the laserbeam.

In FIG. 9A, a coupling unit 900 can include a window (not shown), anozzle module 910 and an air jet module 950. The nozzle module caninclude a nozzle having an opening to form a liquid jet 940. The windowcan be configured to isolate the liquid environment generated by theliquid jet 940 from a dry environment of a laser beam.

The air jet module is coupled to the nozzle module, for example, toaccept the liquid jet 940 generated from the nozzle module, togetherwith forming a gas flow 930 surrounding and separated from the liquidjet. For example, the air jet module 950 can include a double wallconfiguration, such as an inner wall 952 and an outer wall 954. Theinner wall can form a first conduit 922 for accepting the liquid jet topass through. For example, the inner wall can have a hollow cylindershape, with the hollow portion larger than a diameter of the liquid jetfor passing the liquid jet. The hollow cylinder can have a top largeropening for coupling with a cavity 952 in the nozzle module. The hollowcylinder can have a straight conduit portion to guide the liquid jet forforming a laminar flow.

The inner wall and the outer wall can form a second conduit 926surrounding the first conduit. The second conduit can be configured toaccept a gas flow, for example, the outer wall can include a gas inletfor connecting to a gas supply line. The gas flow from the supply linecan generate a gas flow through the second conduit. The gas flow cansurround the liquid jet. The gas flow 930, e.g., the air jet, can flowin a same direction as the liquid jet 940, for example, parallel to theliquid jet flow 940. For example, the inner wall can be configured sothat the gas flow is substantially parallel with the liquid jet. Forexample, the outer surface of the inner wall can be substantiallyparallel to the liquid jet, thus the gas flow can exit the air jetnozzle with a direction substantially parallel to the liquid jet. Theair jet 930 can push the liquid 995 on an object surface 990 so that theliquid jet 940 can interact directly with the object surface withoutencountering any liquid film. The air jet can be generated from a gassupply line, which can include a compressed gas with a pressure lessthan 10 bar, or a compressed gas with a maximum pressure of 10 bar. Thepressure of the gas supply line can be configured to be independentlyadjustable with respect to the liquid jet.

In some embodiments, the inner wall can include at least a hole 923 toprovide fluid communication between the first conduit and the secondconduit. For example, a small amount of gas can enter the cavity 952 ofthe nozzle module to compensate for a vacuum formation due to theformation of the liquid jet. Alternatively, a separate gas flow can beintroduced to the cavity 952 for vacuum compensation.

In some embodiments, one end, e.g., the extreme end that is exposed tothe outside ambient, of the inner wall 952 and/or the outer wall 954 canbe tapered outward. For example, the inner wall 952 can have one end 965forming a tilted surface or a tapered outward surface, which can drainany liquid drop away from the liquid jet 940. The outer wall 954 canalso have one end 960 forming a tilted surface or a tapered outwardsurface. Further, the air jet 930 can attract liquid mist around theliquid jet, thus helping to prevent liquid drops from being pulled tothe liquid jet.

In some embodiments, the inner wall can be longer than the outer wall.For example, the tapered surface 965 can protrude farther than thetapered surface 960. Alternatively, the outer wall can be longer thanthe inner wall. For example, the tapered surface 960 can protrudefarther than the tapered surface 965.

In some embodiments, the inner wall can be configured so that the gasflow is diverged from or converged to the liquid jet. For example, theouter surface of the inner wall can be tapered outward away from theliquid jet, thus the gas flow can exit the air jet nozzle with adirection forming a diverged angle with the liquid jet. The divergedangle can be less than 45, less than 30 degrees, less than 25 degrees,less than 20 degrees, less than 15 degrees, less than 10 degrees, orless than 5 degrees. In some embodiments, multiple air jet nozzles withdifferent diverged angles can be provided, and an air jet nozzle with anappropriate diverged angle can be selected.

In FIG. 9B, an inner wall 952A of the air jet nozzle can have an outwardconical shape, e.g., the outer surface of the conical inner wall 952Acan be configured so that the outer air jet 930A diverges from the innerliquid jet flow 940. The inner wall 952A can have a middle opening for aliquid jet 940 and a surrounded opening for a air jet 930A. The air jet930A can flow in a same direction as the liquid jet 940, for example,diverging from the liquid jet flow 940. The diverged angle, e.g., theangle of the conical surface with the liquid jet flow direction can beless than 45 degrees, such as less than 10, 20, 30 or 40 degrees.

In FIG. 9C, an inner wall 952B can have an inward conical shape, e.g.,the outer surface of the conical inner wall 952B can be configured sothat the outer air jet 930B converges to the inner liquid jet flow 940.The inner wall 952B can have a middle opening for a liquid jet 940 and asurrounded opening for a air jet 930B. The air jet 930B can flow in asame direction as the liquid jet 940, for example, converging to theliquid jet flow 940. The convergence angle, e.g., the angle of theconical surface with the liquid jet flow direction can be less than 45degrees, such as less than 10, 20, 30 or 40 degrees.

Different configurations can be used for the coupling unit for guidingthe air jet. The end surfaces of the coupling unit and the air jetnozzle can be flat or tapered for draining liquid droplets outward(e.g., away from the liquid jet). Different conduit shapes for the airjet can be used, such as concentric conduit for parallel air jet, oroutward curving conduit for outward air jet.

In some embodiments, the present invention discloses a liquid jet guidedlaser system having an air jet nozzle insert for processing a workpiece.The air jet nozzle insert can be provided to a coupling unit to separatethe liquid jet and the air jet. The insert can be exchangeable, allowingdifferent flow configurations for the air jet.

FIG. 10 illustrates a liquid jet guided laser system including acoupling unit having an air jet nozzle according to some embodiments.The liquid jet guided laser system can include a laser system 1010, anda coupling unit 1000 for coupling the laser beam in the laser systemwith the liquid jet. The coupling unit 1000 can include an opticalelement, such as a window 1050, to isolate the liquid 1045 from thelaser system 1010. The laser system 1010 can include a laser beam, whichcan be focused to the liquid, such as to the liquid portion or theliquid jet portion, to form internal reflection in the liquid jet.

The coupling unit 1000 can include a nozzle 1060, which can beconfigured to generate a liquid jet toward a surface of a workpiece1090, together with coupling the laser system to the liquid jet. Forexample, a liquid source can provide a liquid 1045 to a liquid inlet1046. The liquid can form a liquid jet 1040, for example, through anozzle or a nozzle assembly 1060. The nozzle assembly 1060 can include achamber or a cavity 1052 for stabilizing the liquid jet.

The coupling unit can include an air jet nozzle 1021, which can includean inner conduit 1022 for the liquid jet to pass through. The air jetnozzle 1021 can be configured to physically separate the liquid jet froman air jet 1020, such as shielding the liquid jet 1040 from externalinfluence, such as shielding the liquid jet 1040 from the air jet 1020.The air jet nozzle can have a hollow cylinder shape, with the hollowportion larger than a diameter of the liquid jet for passing the liquidjet. The hollow cylinder can have a top larger opening for coupling witha cavity 1052 in the nozzle module. The hollow cylinder can have astraight conduit portion to guide the liquid jet for forming a laminarflow.

The coupling unit can include an air jet nozzle holder 1025, which canalso function as a body or support for the coupling unit. The air jetnozzle 1021 and the air jet nozzle holder 1025 can form an outer conduit1026, which can surround the inner conduit 1022. Gas or gas/liquidmixture 1024 can be provided to the outer conduit 1026, for example,through a gas inlet 1027, to form the air jet 1020. Since the air jetand the liquid jet are physically separated by a partition, e.g., a wallsuch as the air jet nozzle 1021, the air jet and the liquid jet can beindependently from each other, meaning there can be a wide range ofoperating conditions, including pressure and flow, of the air jet thatdo not or minimally affect the operation of the liquid jet. In addition,the direction of the air jet can be adjusted, such as tilted outward sothat the air jet diverges from the liquid jet, higher pressure and flowfor the air jet can be used without affecting the liquid jet.

In some embodiments, the nozzle 1060 can have a cavity 1052 at theoutlet of the nozzle, to optimize the liquid jet, such as to stabilizethe liquid jet. The cavity 1052 can have a low pressure, e.g., lowerthan an outside ambient pressure. The low pressure, e.g., vacuumcondition, can generate some turbulence in the liquid jet formation.

In some embodiments, the present invention discloses providing a gas tothe cavity of the nozzle to compensate for the vacuum pressure. The gascan be provided from a gas source, or from the air jet. For example, ahole 1023 in the air jet nozzle can reduce the vacuum level, e.g.,increasing the pressure, in the cavity 1052 of the nozzle area. The airjet can be generated from a gas supply line, which can include acompressed gas with a pressure less than 10 bar, or a compressed gaswith a maximum pressure of 10 bar. The pressure of the gas supply linecan be configured to be independently adjustable with respect to theliquid jet.

The air jet can be generated from a gas supply line, which can include acompressed gas with a pressure less than 10 bar, or a compressed gaswith a maximum pressure of 10 bar. The pressure of the gas supply linecan be configured to be independently adjustable with respect to theliquid jet.

In some embodiments, one end 1070 of the air jet nozzle can be taperedoutward, forming an outward tilted surface or a tapered outward surface,which can drain any liquid drop away from the liquid jet 1040. One end1072 of the air jet nozzle holder can also be tapered outward, formingan outward tilted surface or a tapered outward surface, which can drainany liquid drop away from the liquid jet 1040. The air jet nozzle can belonger than the air jet nozzle holder, e.g., there is a distance 1075between an end of the air jet nozzle and an end of the air jet nozzleholder.

FIGS. 11A-11D illustrate a schematic of a coupling unit for liquid jetguided laser processing according to some embodiments. FIG. 11A shows across section of the coupling unit, and FIGS. 11B-11D show perspectiveviews of different air jet nozzle 1170, 1172, and 1174 in the couplingunit. A transparent window 1120 can be used to separate the dry portionof a laser beam 1110 and the liquid portion of a liquid jet 1140. A lens(not shown) can be used to focus the laser beam 1110 onto the liquidjet. A nozzle 1150 can be coupled to the window 1120, leaving a smallgap for accepting a liquid, such as water, from a liquid source 1145.The coupling unit has a opening in the middle for the liquid to exit asa liquid jet 1140. The nozzle is open at an opposite end to form acavity 1152, which can improve the laminar flow of the liquid jet 1140.

An air jet nozzle 1170 can be coupled to the nozzle 1150, for example,closing the cavity 1155 and guiding the liquid jet 1140 to the exit. Theair jet nozzle 1170 can be shaped at the outside to generate a gas flow1130 from a gas source 1135. The air jet nozzle can surround the liquidjet, and form the air jet 1130 in a parallel direction. Thus the air jetnozzle 1170 can be configured to provide a parallel and surrounding airjet 1130 with respect to the liquid jet 1140. The air jet nozzle canform a partition between the air jet 1130 and the liquid jet 1140, e.g.,the liquid jet and the air jet exit the coupling unit at two separatenozzle openings. The air jet nozzle can provide a separation, which canallow for the independent control of the air jet, e.g., controlling thepressure and flow rate to achieve an optimum surface clearing processwhile not interfering with the liquid jet operation.

Different air jet nozzles are shown in FIGS. 11B-11D. In FIG. 11B, anair jet nozzle 1170 can have a vertical outer surface, e.g., a surfaceparallel with the vertical flow of the liquid jet, such that the angle1190 of the outer surface and the liquid jet flow direction is aboutzero. In FIG. 11C, an air jet nozzle 1172 can have an outward verticalouter surface, e.g., a surface making a diverged angle with the verticalflow of the liquid jet, such that the angle 1192 of the outer surfaceand the liquid jet flow direction is greater than zero. The direction ofthe angle is such that the air jet is diverged from the liquid jet whenhitting the object surface. In FIG. 11D, an air jet nozzle 1174 can havean inward vertical outer surface, e.g., a surface making a convergedangle with the vertical flow of the liquid jet, such that the angle 1194of the outer surface and the liquid jet flow direction is greater thanzero. The direction of the angle is such that the air jet is convergedwith the liquid jet in the direction of the object surface. Theconvergent air jet can be close to, but not interfere with, the liquidjet when hitting the object surface.

The bottom 1157 of the air jet nozzle can be tapered outward, forexample, to guide any liquid droplets away from the liquid jet forminimal interference with the liquid jet. Similarly, the bottom 1159 ofthe coupling unit bottom portion 1155 can also be tapered outward, e.g.,away from the central portion that houses the liquid jet.

In some embodiments, the air jet 1130 can be configured to attract orlead liquid mist away from the liquid jet 1140. For example, the taperedsurfaces 1157 and 1159 can be effective for large liquid droplets, butcan be less effective for smaller droplets, such as liquid mist, whichmight occur far from the tapered surfaces. The air jet can thus guidethe liquid mist away from the liquid jet, for example, preventing theliquid mist from cumulating and potentially disrupting the liquid jetoperation.

FIG. 12 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments. Operation 1200 supplies a liquidto a nozzle module to form a liquid jet, wherein the liquid jet isconfigured to pass through a first conduit formed by an inner wall of anair jet module. Operation 1210 focuses a laser beam to form internalreflection in at least a portion of the liquid jet. Operation 1220supplies a gas flow to form an air jet in a second conduit, wherein thesecond conduit is formed between the inner wall and an outer wall of theair jet module, wherein the air jet is configured to surround the liquidjet, wherein the air jet and the liquid jet are guided toward aworkpiece.

FIG. 13 illustrates a flow chart for operating a liquid jet guided lasersystem according to some embodiments. Operation 1300 supplies a liquidto a nozzle to form a liquid jet, wherein the liquid jet is configuredto pass through a first conduit inside an air jet nozzle. Operation 1310focuses a laser beam to form internal reflection in at least a portionof the liquid jet. Operation 1320 supplies a gas flow to a secondconduit between an outside of the air jet nozzle and an inside of an airjet nozzle holder to form an air jet, wherein the air jet is configuredto surround the liquid jet, wherein the air jet nozzle is configured toshield the liquid jet from the air jet, wherein the air jet and theliquid jet are guided toward a workpiece.

FIGS. 14A-14B illustrate a coupling unit for a liquid jet guided lasersystem according to some embodiments. A coupling unit 1401 can bemanufactured as CNC-milled metal part. On the top side there is a coneshaped entrance 1402 for the laser beam. Below the cone shaped entrance1402 is the laser window 1403. The gap between laser the window 1403 andnozzle 1404 is filled with liquid by a drilled hole 1405. The nozzle1404 is held in place by a counter screw 1406 that is mounted from thebottom side of the coupling unit 1401. Between the counter screw 1406and the nozzle 1404, a flow-insert 1407, e.g., an air jet nozzle, ismounted. The flow-insert 1407 has a concentrically drilled center hole1408 through which the liquid-jet 1409 passes and that mechanicallyseparates the liquid-jet 1409 from the air jet 1410, which is providedby a separate drilled hole 1415 inside the coupling unit 1401. Thismechanical separation inside the coupling unit 1401 generates aconcentric and in-direct air jet 1410 flow column around the liquid-jet1409 that exists both inside and outside/below of the coupling unit1401. Furthermore, the flow-insert 1407 inlet connection to the drilledhole 1415 for air jet inside the coupling unit is shaped in such waythat the air jet 1410 flow direction is downwards in the same directionas the liquid-jet 1409.

Both the counter screw 1406 and the flow-insert 1407 have a convex orconical shape on the exit side. The convex or conical shape is used toguide cumulated liquid mist drops away from the liquid-jet 1409. Thedownward air jet 1410 flow works as a barrier column around theliquid-jet 1409 and actively blows away liquid mist drops, which arenear the center of the counter screw 1406. Holes 1411 can be provided inthe flow-insert 1407 for equilibrating the pressure in the cavity at thenozzle 1404.

In some embodiments, the air jet can be used with the assist gas. Theassist gas can optimize the liquid jet laminar flow length, such asincreasing the stability of the liquid jet flow, resulting in a longerstable liquid jet. The assist gas can surround the liquid jet, and canbe prepared in a same cavity area and can exit at a same opening. Theair jet can prepare the object surface, such as clearing any accumulatedliquid from the surface. The air jet can also surround the liquid jet(and the assist gas), and can be prepared in a separate area for exitingthe coupling unit at different openings for minimum interference.

FIG. 15 illustrates a schematic of a coupling unit for liquid jet guidedlaser processing according to some embodiments. A transparent window1520 can be used to separate the dry portion of a laser beam 1510 andthe liquid portion of a liquid jet 1540. A lens (not shown) can be usedto focus the laser beam 1510 onto the liquid jet. A nozzle 1550 can becoupled to the window 1520, leaving a small gap for accepting a liquid,such as water, from a liquid source 1545. The nozzle has a opening inthe middle for the liquid to exit as a liquid jet 1540. The nozzle isopen at an opposite end to form a cavity 1552, which can improve thelaminar flow of the liquid jet 1540.

An assist gas flow 1580 can be introduced to the cavity 1552, forexample, from a gas source 1585. The assist gas flow 1580 can flowtoward the liquid jet, and then envelop the liquid jet toward the exit.The assist gas can be adjusted, e.g., having lower pressure and/or flow,to provide an active vacuum compensation in the cavity. A vacuum can bebuilt up by the liquid-jet pressure in the cavity 1552, which can affectthe liquid jet operation, such as causing instability to the liquid jet.

An air jet nozzle 1570 can be coupled to the coupling unit, for example,closing the cavity 1555 and guiding the liquid jet 1540 to the exit. Theair jet nozzle 1570 can be shaped at the outside to accept a air jet1530 from a gas source 1535. The air jet nozzle can surround the liquidjet, and accept the air jet 1530 in a parallel direction. Thus the airjet nozzle can be configured to provide a parallel and surrounding airjet 1530 with respect to the liquid jet 1540. The air jet nozzle canform a solid partition between the air jet 1530 and the liquid jet 1540,e.g., the liquid jet and the air jet exit the coupling unit at twoseparate nozzle openings. The air jet nozzle can provide a solidseparation, which can allow for the independent control of the air jet,e.g., controlling the pressure and flow rate to achieve an optimumsurface clearing process while not interfering with the liquid jetoperation.

As shown, the air jet nozzle 1570 has a parallel outer surface toprovide a parallel air jet, e.g., air jet running in a paralleldirection as the liquid jet. Other configurations can be used, such asdivergent or convergent outer surfaces to provide diverged or convergedair jet, e.g., air jet running in a same direction, but not parallel, asthe liquid jet.

FIGS. 16A-16B illustrate flow charts for operating a liquid jet guidedlaser beam using a air jet according to some embodiments. In FIG. 16A,operation 1600 flows a liquid to a coupling unit to form a liquid jet.Operation 1610 focuses a laser beam onto the liquid jet, forming aliquid jet guided laser beam. Operation 1620 forms a gas flow running inthe same direction such as parallel to the liquid jet. The gas flow isseparate from the liquid jet by a solid partition. The gas flow isconfigured to clear a surface that the liquid jet is to be contacted. Insome embodiments, the gas flow is configured to be surrounding theliquid jet, in a same flow direction as the liquid jet.

In FIG. 16B, operation 1630 provides an air jet nozzle to a couplingunit, wherein the coupling unit is operable for forming a liquid jet.Operation 1640 forms a laser beam guided by the liquid jet. Operation1650 forms a gas flow running in the same direction such as parallel tothe liquid jet. The gas flow is separate from the liquid jet by the airjet nozzle.

In some embodiments, the present invention discloses methods to keep awork piece surface free from liquid accumulation while performingliquid-jet guided laser based material processing. The methods can use aconcentric air jet column around the liquid-jet. The air jet can beguided concentrically in the same direction as the liquid-jet by a flowmechanism that mechanically separates the air jet from the liquid-jet.The liquid-jet and the air jet leave the coupling unit through aseparate exit. Both the separation and flow direction between the airjet column and the liquid-jet remain intact also outside the couplingunit while being directed to the work piece. The pressure of the air jetcan be independently controlled and adjustable, e.g., depending on theshapes of work piece. Any gas can be used as the air jet, such as air orclean dry air. The air jet can be operable to reduce of the dynamicfriction between the liquid jet, such as water, and the ambient gas,such as air. The air jet can be configured to provide protection liquidaccumulated from liquid mist to fall into the liquid jet.

In some embodiments, the present invention discloses apparatuses to keepa work piece surface free from liquid accumulation while performingliquid-jet guided laser based material processing. The apparatuses caninclude an air jet mechanism, which can include an interchangeable airjet nozzle that is located below the nozzle. The interchangeable air jetnozzle can allow variable lengths of the flow mechanism to fitindividual work piece processing requirements.

The mechanical flow mechanism can be configured to guide the air jet andto separate it from the liquid-jet. The mechanical flow mechanism cancontain one or multiple venting holes, which connect the nozzle chamberwith the air jet flow, so that the vacuum that would build up by theliquid-jet pressure below the nozzle inside the coupling unit, can becompensated by the available air jet, which is pulled towards the nozzleby the vacuum.

In some embodiments, the shape of the exit side of both the couplingunit counter screw as well as the air jet mechanism is convex or conicalin order to guide cumulated liquid mist drops away from the centerdrilled hole and therewith away from the liquid-jet.

In some embodiments, the cavity in the coupling unit can form a vacuumbelow the opening that the liquid flows into to form the liquid jet. Thevacuum can affect the liquid jet operation, such as causing instabilityto the liquid jet. To avoid the creation of a vacuum below the nozzle,the cavity can be provided with pathways to an outside ambient forequilibrate the pressure. For example, the air jet nozzle can containmultiple vertically oriented small drilled holes on the top side of thepart, which connect the nozzle cavity with the air jet. The direction ofthe small drilled holes can be under an angle between −45° to +45° inrespect to the normal of the air jet nozzle, so that the air jet is notactively guided into the nozzle chamber, but merely functions as anopening through which the nozzle chamber can pull new gas by theliquid-jet generated vacuum.

FIGS. 17A-17B illustrate a schematic of another coupling unit for liquidjet guided laser processing according to some embodiments. FIG. 17Ashows a cross section of the coupling unit, and FIG. 17B showsperspective views of the air jet nozzle 1770 in the coupling unit. Atransparent window can be used to separate the dry portion of a laserbeam and the liquid portion of a liquid jet 1740. A nozzle 1750 can becoupled to the window 1720, leaving a small gap for accepting a liquidfrom a liquid source. The nozzle has a opening in the middle for theliquid to exit as a liquid jet 1740. The nozzle is open at an oppositeend to form a cavity 1752, which can improve the laminar flow of theliquid jet 1740.

An air jet nozzle 1770 can be coupled to the nozzle, for example,closing the cavity 1752 and guiding the liquid jet 1740 to the exit. Theair jet nozzle 1770 can be shaped at the outside to accept a air jet1730 from a gas source 1735. The air jet nozzle can surround the liquidjet, and accept the air jet 1730 in a parallel direction. The air jetnozzle 1770 can have one or more small holes 1775, which connect thecavity area 1752 with the air jet 1730. The holes 1775 can equalize thepressure in the cavity area with the outside pressure, thus can reduceor eliminate any vacuum creation in the cavity area.

As shown, the air jet nozzle 1770 has a parallel outer surface toprovide a parallel air jet, e.g., air jet running in a paralleldirection as the liquid jet. Other configurations can be used, such asdivergent or convergent outer surfaces to provide diverged or convergedair jet, e.g., air jet running in a same direction, but not parallel, asthe liquid jet.

FIG. 18 illustrates a schematic of another coupling unit for liquid jetguided laser processing according to some embodiments. A transparentwindow can be used to separate the dry portion of a laser beam and theliquid portion of a liquid jet 1840. A nozzle 1850 can be coupled to thewindow 1820, leaving a small gap for accepting a liquid from a liquidsource. The nozzle has a opening in the middle for the liquid to exit asa liquid jet 1840. The nozzle is open at an opposite end to form acavity 1852, which can improve the laminar flow of the liquid jet 1840.

An assist gas flow 1880 can be introduced to the cavity 1852, forexample, from a gas source. The assist gas flow 1880 can flow toward theliquid jet, and then envelop the liquid jet toward the exit. The assistgas can be adjusted, e.g., having lower pressure and/or flow, to providean active vacuum compensation in the cavity. A vacuum can be built up bythe liquid-jet pressure in the cavity 1852, which can affect the liquidjet operation, such as causing instability to the liquid jet.

An air jet nozzle 1870 can be coupled to the nozzle, for example,closing the cavity 1855 and guiding the liquid jet 1840 to the exit. Theair jet nozzle can surround the liquid jet, and accept the air jet 1830in the same direction such as a parallel direction. Thus the air jetnozzle can be configured to provide a parallel and surrounding air jet1830 with respect to the liquid jet 1840. The air jet nozzle 1870 canhave one or more small holes 1875, which connect the cavity area 1852with the air jet 1830. The holes 1875 can equalize the pressure in thecavity area with the outside pressure, thus can reduce or eliminate anyvacuum creation in the cavity area.

As shown, the air jet nozzle 1870 has a parallel outer surface toprovide a parallel air jet, e.g., air jet running in a paralleldirection as the liquid jet. Other configurations can be used, such asdivergent or convergent outer surfaces to provide diverged or convergedair jet, e.g., air jet running in a same direction, but not parallel, asthe liquid jet.

FIGS. 19A-19B illustrate flow charts for operating a liquid jet guidedlaser system according to some embodiments. In FIG. 19A, operation 1900flows a liquid to a cavity area. The liquid exits from the cavity in aform of a liquid jet. The liquid jet contains a laser beam. Operation1910 equalizes the pressure in the cavity by a fluid passage way betweenthe cavity and a gas flow pathway.

In FIG. 19B, operation 1930 provides an air jet nozzle to a couplingunit. The coupling unit is operable for forming a liquid jet. Operation1940 forms a laser beam guided by the liquid jet. Operation 1950 forms agas flow running in the same direction such as parallel to the liquidjet. The gas flow is separate from the liquid jet by the air jet nozzle.Operation 1960 equalizes the pressure in the coupling unit by a fluidpassage way between the coupling unit and the gas flow pathway.

What is claimed is:
 1. A liquid jet guided laser system comprising: alaser for emitting a laser beam; a first nozzle module for forming aliquid jet from a liquid supply line; an optical element for introducingthe laser beam into the liquid jet; a second nozzle module comprising afirst gas inlet connected to one or more gas supply lines to form afirst gas flow, wherein the first gas flow is an assist gas, and theliquid jet with the assist gas exits out of the second nozzle modulethrough a first exit; a third nozzle module comprising a second gasinlet connected to one or more gas supply lines to form a second gasflow, wherein the second gas flow is an air jet; the second nozzlemodule and the third nozzle module form a second conduit between thesecond nozzle module and the third nozzle module; the air jet passesthrough the second conduit and exits out of a second exit formed betweenthe second nozzle module and the third nozzle module; the air jet exitsseparately from the laser and liquid jet with assist gas; the air jetsurrounds the laser and the liquid jet with assist gas.
 2. The system,as in claim 1, wherein: the first nozzle module and the second nozzlemodule form a first conduit between the first nozzle and the secondnozzle module; the liquid jet and the assist gas pass through the firstconduit, through the second nozzle module and exit out the first exitformed in the second nozzle module.
 3. The system, as in claim 2,wherein: the first conduit flows the assist gas toward the liquid jet,wherein the assist gas envelops the liquid jet when exiting the firstexit in the second nozzle module.
 4. The system as in claim 2, wherein:the first conduit is shaped to improve the laminar flow of the liquidjet.
 5. The system, as in claim 1, wherein: the first nozzle module isremovably coupled to the optical element.
 6. The system, as in claim 1,wherein: the second nozzle module is removably coupled to the firstnozzle.
 7. The system, as in claim 1, wherein: the third nozzle moduleis removably coupled to the second nozzle.
 8. The system as in claim 1,wherein: the second nozzle module exterior surface cross section isparallel to the liquid jet with assist gas center plane, such that theair jet is parallel with the liquid jet with assist gas on exit.
 9. Thesystem as in claim 1, wherein: the second nozzle module exterior surfacecross section is divergent to the liquid jet with assist gas centerplane, such that the air jet is divergent with the liquid jet withassist gas on exit.
 10. The system as in claim 1, wherein: the secondnozzle module exterior surface cross section is convergent to the liquidjet with assist gas center plane, such that the air jet is convergentwith the liquid jet with assist gas on exit.
 11. The system as in claim1, wherein: the air jet exits the second exit at an angle between −90and +90 degrees in respect to the liquid jet with assist gas direction.12. The system, as in claim 1, wherein: the second exit is structurallyisolated from the first exit, such that the air jet does not interferewith the liquid jet with assist gas on exit.
 13. The system, as in claim2, wherein: the first conduit with the first exit and the second conduitwith the second exit are structurally and fluidically isolated from eachother.
 14. The system, as in claim 2, wherein: the first conduit withthe first exit and the second conduit with the second exit arestructurally isolated from each other but are configured with fluidcommunication paths for vacuum compensation in the first conduit. 15.The system, as in claim 1, wherein: the assist gas has an assist gaspressure and flow that is able to be adjusted respectively to provideactive vacuum compensation in the conduit.
 16. The system as in claim 1,wherein: the air jet has an air gas pressure and flow that is able to beadjusted respectively to achieve an optimum surface clearing process.17. The system as in claim 1, wherein: the air jet has an air gaspressure and flow that is able to be adjusted respectively such that theair jet does not interfere with the liquid jet.
 18. The system as inclaim 17, wherein: the air gas pressure is less than 10 bar.
 19. Thesystem as in claim 1, wherein: the first gas inlet is connected to arespective first gas supply and the second gas inlet is connected to arespective second gas supply.
 20. The system as in claim 1, wherein: theair jet reduces at least one of the following: an amount liquid at asurface of a workpiece, wherein the air jet keeps the surface dry tooptimize the efficiency of the liquid jet and guided laser beam; a backreflection of the liquid jet in the direction of the nozzles isminimized or eliminated, wherein the air jet increases the liquidquality of the liquid jet at the contact point to the surface; a liquidmist and a liquid drop accumulated on the nozzles from the liquid mist.